1. Field of the Invention
The present invention relates to a sheet conveying and sorting system and, in particular, to such sheet conveying and sorting system which sorts sheets such as paper, film, metal foil or the like and collects the sheets by a given number of sheets (which can also be referred to as a package unit of sheets).
2. Description of the Related Art
Generally, after a long web of paper, film, metal foil or the like is cut into sheets, the sheets are collected by a given number of sheets (which will hereinafter be referred to as a package unit of sheets as well) and are then shipped. And, a sheet conveying/sorting system which sorts the sheets by the package unit includes mainly the following types:
A first type is a sheet conveying/sorting system which is shown in FIG. 12. As shown in FIG. 12, a long web 12 sent out from a roll 10 is cut by a cutter 14 into predetermined length of sheets 16. The thus cut sheets 16 are then sorted by a sheet sorting gate 18 of the sheet included in the sheet conveying/sorting system into two passages, that is, an upper conveying passage 20 and a lower conveying passage 22. By means of this, the sheets 16 can be collected by the package units into an upper collecting part 24 and a lower collecting part 26 alternately.
In a second type of sheet conveying/sorting system, the sheets are gated out at the reduced sheet cutting speed to a reject gate provided downstream of a cutting part to thereby obtain a switch time for sorting the sheets, and the sorted sheets are then collected by the package units.
A third type of sheet conveying/sorting system includes in the collecting part thereof a fork for sorting the sheets and the third type system is able to sort the sheets by the package units by advancing and retreating the fork. (Refer to Japanese Patent Application Laid-Open (Tokkai) No. 55-40137, No. 57- 27860, and No. 2-70660).
In a fourth type of sheet conveying/sorting system, there is disposed a stopper in the middle of a conveying passage, the sheets are held by and between the stopper and the conveying passage, the sheets are stopped so the distance between the sheets being conveyed on and the sheets being stopped is increased, and then the sheets are sorted by the package units (see Japanese Patent Application Laid-Open (Tokkai) No. 1-294164).
A fifth type of sheet conveying/sorting system includes an inside conveyor and an outside conveyor which is disposed along the outer periphery of the inside conveyor. And, a holding conveyor is disposed above the outside conveyor. While sheets being moved are being held by and between the outside and holding conveyors, the speed of the inside conveyor is increased to widen the distance between the sheets being held and the sheets being carried on the inside conveyor, so that the sheets can be sorted by the package units (see Japanese Patent Application Laid-Open (Tokkai) No. 2-127355).
However, in the first type of sheet conveying and sorting system, since the sheets 16 are sorted into the upper conveying passage 20 and lower conveying passage 22, at least two conveying passages for sorting are necessary. This results in the increased manufacturing cost and also requires a large installation space.
Also, in the second type of sheet conveying/sorting system, the gating-out of the sheets leads to the lowered rate of the quantity of sheets that is theoretically expected in a production process and at the same time, because the sheets are sorted by reducing the sheet cutting speed, a production efficiency is lowered as well.
Further, referring now to the third and fourth types of sheet conveying/sorting systems, because the third type sorts the sheets by use of the fork, and because the fourth type sorts the sheets while the sheets are being held by and between the stopper and conveying passage, there is a possibility that the sheet conveying attitude or the positional relationship between the sheets can be disturbed or that, when the sheet has a soft surface, the sheet surface can be abraded. In addition, these types of systems are disadvantageous in that the sheets conveying operation thereof is not stable.
Moreover, in the fifth type of sheet conveying/sorting system, since the leading end of the sheet held by and between the inside and holding conveyors may be rubbed against the inside conveyor, the soft sheet surface can be abraded. Also, the fifth type system finds it hard to adapt itself to a small package.